1. Field of the Invention
One disclosed aspect of the embodiments relates to a mark detection system in an imprint apparatus configured to transfer a pattern of a mold onto an imprint material on a substrate.
2. Description of the Related Art
An imprint technique is a technique for bringing a minute pattern formed on a mold and an imprint material supplied on a substrate into contact with each other (imprinting the pattern) to thereby form the pattern.
An optical imprint method will be described now as one example of the imprint technique. First, a layer constituted by photo curable resin (hereinafter referred to as “imprint resin”) is formed on a substrate (for example, a semiconductor wafer). Subsequently, the imprint resin and a mold with a desired minute uneven structure (pattern) formed thereon are brought into contact with each other. Subsequently, while the imprint resin and the mold are kept in contact with each other, the imprint resin is cured by be irradiated with ultraviolet light. After the imprint resin is cured, the imprint resin and the mold are separated from each other, thereby forming the pattern on the substrate.
An imprint apparatus performs alignment for each shot before bringing the mold and the imprint resin into contact with each other. The alignment of the imprint apparatus is realized by using a through-the-mold detection system (hereinafter referred to as “TTM detection system”), which may perform alignment by simultaneously detecting marks formed on the mold and the wafer. Japanese Patent Application Laid-Open No. 2005-286062 discusses an imprint apparatus in which an illumination system for irradiating a resin layer with ultraviolet light is arranged above a mold, and a TTM detection system is arranged in such a manner that the TTM detection system gets out of the way of the illumination system.
It is required to arrange the TTM detection system to be inclined relative to an optical axis of the illumination system to prevent the TTM detection system from interfering with the illumination system and a illumination light flux. To enable wafer alignment by the TTM detection system arranged to be inclined relative to the optical axis of the illumination system, the TTM detection system is arranged according to the Littrow arrangement, and detects a signal by acquiring light diffracted at a Littrow angle. However, the TTM detection system arranged according to the Littrow arrangement cannot have a sufficiently large detection numerical aperture (hereinafter referred to as “NA”) of the TTM detection system for the configurational limitation, leading to a problem of a reduction in the detection light amount, thereby resulting in low alignment accuracy.